Most sensory regions of the brain receive extensive inputs from other central structures in addition to input from the periphery and most such regions show some form of plasticity. But the functional significance of the central inputs and plasticity are only poorly understood. This study seeks insights into these general issues by examining the electrosensory lobe (ELL) of mormyrid electric fish in which: the sensory inputs can be precisely controlled; the central inputs are relatively well understood; and plasticity has been established at both the systems and synaptic levels. The ELL is a cerebellum-like structure that receives the primary afferent input from electroreceptors as well as afferent input from various central structures. The ELL and similar structures in other fish are adaptive sensory processors in which memory-like predictions about sensory input are generated and subtracted from current sensory input allowing novel inputs to stand out. The predictions being based on prior associations between peripheral and central inputs. The central input in mormyrid fish that has been examined most extensively with regards to its effects and plasticity is an electric organ corollary discharge signal (EOCD) associated with the motor command that drives the EOD. Specific aims of the project are: 1) To determine responses of ELL cells to electrosensory stimuli, to the EOCD and to electrical activation of central afferents. 2) To determine the plasticity of ELL cells' responses to natural activation of other types of descending central afferents besides the EOCD. 3) To determine the circuitry and cellular mechanisms responsible for the plasticity of EOCD responses in ELL cells. 4) To determine the response properties of the central afferents to the ELL; and 5) To determine the anatomical connections of a major source of central input to the ELL. The primary method will be intracellular recording of cells in ELL and in central structures projecting to ELL together with intracellular staining for morphological identification. The results are expected to be a source of hypotheses into the central processing of sensory information in general as well as into the processing of information in other cerebellum-like structures.